1. Field of the Invention
The present invention relates to an optical signal amplifier for compensating the attenuation of optical signals during transmission and, more particularly, to an optical signal amplifier capable of being hybridly integrated, an optical communication module comprising the amplifier, and a method for fabricating the amplifier.
2. Description of the Related Art
Optical communication modules are less competitive in price and size if assembled from discrete optical devices, each requiring a separate package to perform a specific function in an optical communication system. To improve the price competitiveness, integration technologies are being applied to optical devices. Two primary integration technologies are hybrid integration and monolithic integration. The hybrid integration is an optical platform technology that integrates active optical devices on a platform, which is integrated with the functions of passive devices using a PLC (planar lightwave circuit) technology. In contrast, the monolithic integration is a system-on-chip technology that monolithically integrates all optical and optoelectronic components, excluding a laser diode, into a single chip through a CMOS process. Although monolithic integration achieves a much higher degree of integration, it requires sophisticated expertise. Accordingly, studies have been more actively made into hybrid-integration technologies.
An optical signal transmitted along an optical transmission line is typically changed to a reduced level of power due to optical loss of power. Once the power of the optical signal is reduced below a certain point where a receiver is unable to detect the signal, a communication error occurs. To address this problem, an optical amplifier is arranged between the transmitter and the receiver for the amplification of optical signals, thereby enabling signal transmission over long distances with fewer errors.
The most commonly-used amplifier is EDFA (erbium-doped fiber amplifier), which uses a silica glass fiber doped with a rare-earth element (for example, Er). EDFA amplifies an inputted optical signal by the excitation of the doped rare-earth element using a pumping light and outputs the amplified signal. However, EDFA using an optical fiber is not suitable for hybrid integration. Further, EDFA is expensive because it uses laser having a high output over 100 mW as a pumping light source.